U.S. Army Airborne slang for the phenomenon in which one has to shit so badly it could blow at any moment.

Having 'Jumpers in the door' is an emergency situation usually characterized by a frantic race to the toilet, and in which if a bathroom facility is not located immediately a huge mess in one's underwear could occur.

The actual phrase is coined after a chalk of U.S. Army paratroopers awaiting the green light during an Airborne operation, so they may exit the aircraft -- particularly the number 1 jumper who is waiting directly in front of the door for the light to change.